First, make the sauce: Boil and peel tomatoes, blend them with water, garlic, cumin, and pepper. Cook the sauce with a bit of oil in a pot until it thickens.
Make the potato mixture. Boil potatoes until fork-tender, peel them and mash them into a bowl. Mix with cheese, paprika, cumin, pepper, salt, and garlic powder.
Assemble. Lay one tortilla flat and fill half with a spoonful of the potatoes mixture. Fold in half and press down lightly. Make as many as you can until all potato mixture is used.
Fry. Fry "tacos de papa" in hot oil until golden and crispy. About 2 minutes per side.
Serve. With plenty of tomato sauce, onion, lettuce, and cheese. If you like spicy food, add also your favorite Mexican salsa!